This proposal seeks support for the career development of Luz Claudio, Ph.D., Assistant Professor in the Mount Sinai School of Medicine, through a mentored research experience with Dr. David R. Colman, Professor of Molecular Biology at Mount Sinai. Her previous findings suggested that brain endothelial cells de-differentiate when the blood-brain barrier (BBB) is disrupted. When cultured in vitro, endothelial cells lose the capacity to form impermeable tight junctions, a critical feature of the BBB. This project has two goals. The first is to develop an accurate, reliable and easy to maintain in vitro BBB system that would have numerous applications for the study of the transport mechanisms of therapeutic drugs and understanding of neuropathological mechanisms. To achieve this goal, we will first determine what are the gene products related to intracellular adhesion that are important in the formation of the BBB in vitro when endothelial cells are exposed to astrocyte-conditioned media. This information will be used to guide the development of an in vitro model of the BBB. For this, endothelial cells will be transfected in culture with protein zero (P0) an obligatory adhesion molecule that initially forces the plasma membranes into close apposition and then triggers formation of intercellular junctions. Previous experiments in HeLa cells, a carcinoma cell line, and preliminary experiments in endothelial cells show that P0 induced the formation of junctions between transfected cells. In HeLa cells, P0 induces the expression of normal junctional components and increases cellular differentiation while not forming part of the junctional structure. Once intercellular adhesion has been induced in endothelial cells, the functional and structural characteristics of the transfectants will be analyzed and compared with the data obtained from endothelial cells induced to form a BBB by exposure to astrocyte-conditioned media. The second goal of this application is the career development of Dr. Claudio, a young minority investigator, by broadening her skills using a molecular biology approach. It is expected that Dr. Claudio will obtain a closely mentored career development experience that will enhance her opportunities to establish an independent research program to address issues related to the role of the BBB in mental and neurological disease.